π§ Machine Learning
Research on probabilistic graphical models, neural networks, natural language processing, adversarial ML, and classification methods.
Machine learning algorithms use experience to improve their performance on a given task. In practice, "experience" is understood as data, and performance is measured according to the task at hand. Our research in machine learning spans both fundamental methods and their applications to complex real-world problems.
Probabilistic Graphical Models (PGMs)
Bayesian Networks & Markov Networks
Research on learning the structure and parameters of Bayesian networks and Markov networks from data. Applications to density estimation, anomaly detection, classification, and generation of synthetic data.
Restricted Boltzmann Machines (RBMs)
Investigation of structural restricted Boltzmann machines for image denoising and classification. Research on the synergies between energy-based models and probabilistic graphical models.
Vine Copulas
Research on vine copula models as flexible multivariate dependency structures. Development of algorithms for learning the graph structure of regular vine-copulas from dependence data. Applications to machine learning tasks requiring accurate joint distribution modeling.
Copula-based Classification
Use of copula functions for classification and regression tasks. Vine copulas provide flexible alternatives to standard Gaussian assumptions for modeling complex multivariate distributions.
Neural Networks & Deep Learning
Neural Architecture Search (NAS)
Research on evolutionary and learning-based methods for automatically designing neural network architectures. Includes factorized model representations, heterogeneous multi-network architectures, and the interplay between NAS components and variation operators.
Generative Models (GANs & VAEs)
Research on generative adversarial networks and variational autoencoders, including their training dynamics, transferability, and optimization using gradient-based methods.
Physics-Informed Neural Networks (PINNs)
Development and analysis of physics-informed neural networks for solving partial differential equations arising in fluid dynamics. Research on hyperparameter influence, generalization behavior outside the training domain, and second-order optimization with domain decomposition.
Semi-Supervised Learning
Neuroevolutionary algorithms guided by neuron coverage metrics for semi-supervised classification. Combining evolutionary search with coverage-based objectives to improve learning with limited labeled data.
Neural Networks for Physical Systems
Application of neural networks (including NAS) to identify phase transitions in physical systems such as the Ising model. Research on the capabilities of neural networks for computational physics tasks.
Natural Language Processing (NLP)
Multi-label Hierarchical Classification
Development of multi-dimensional hierarchical classification methods for NLP tasks. Research on characterization, solving strategies, and performance measures for complex hierarchical label spaces.
Large Language Models (LLMs) for Feature Selection
Exploration of LLMs as tools for feature selection and anomaly classification. Stacking predictions from multiple LLM models to improve accuracy and explainability in industrial anomaly detection tasks.
ENIA Chair in AI & Language Technology
Participation in the ENIA (National Artificial Intelligence Strategy) Chair at UPV/EHU (HiTZ Center) focused on artificial intelligence and language technology. Research, teaching, and knowledge transfer in AI for language.
Adversarial Machine Learning & Explainability
Adversarial Attacks in Explainable ML
Comprehensive survey and research on adversarial threats against explainable machine learning systems. Identifying vulnerabilities in model explanations and developing defenses against attacks targeting interpretability.
Adversarial Class Probability Distributions
Extension of adversarial attack methods to produce adversarial class probability distributions, going beyond misclassification to manipulate the confidence scores output by classifiers.
Adversarial Examples in Audio
Research on generating and defending against adversarial examples in the audio domain. Investigation of the transferability, robustness, and perceptibility of adversarial audio perturbations.
Probabilistic Self-Explainable Neural Networks
Development of uncertainty-aware explanations through probabilistic self-explainable neural networks, providing calibrated confidence estimates for model predictions and their explanations.
Classification, Regression & Data Augmentation
Classification from Time Series
Classification of household devices from electricity usage time series; fault classification in building thermal systems (fan coil units). Research on the impact of imputation methods and temporal features.
Feature Selection Methods
Filter method-based feature selection for multi-target regression problems, including scenarios with unattributed identities. Feature selection and causality explanation for anomaly classification in building systems.
Random Vector Functional Link Networks
Research on random vector functional link forests and extreme learning forests applied to UAV automatic target recognition. Evaluation of ensemble methods for classification under challenging conditions.
Selected Publications
- Garciarena U and Santana R (2017). An extensive analysis of the interaction between missing data types, imputation methods, and supervised classifiers. Expert Systems with Applications.
- Garciarena U, Perfecto C and Santana R (2017). Evolving imputation strategies for missing data in classification problems with TPOT. GECCO 2017.
- Garciarena U, Santana R and Mendiburu A (2018). Evolved GANs for generating Pareto set approximations. GECCO 2018.
- Garciarena U, Santana R and Mendiburu A (2018). Analysis of the complexity of the automatic pipeline generation problem. CEC 2018.
- Garciarena U, Santana R and Mendiburu A (2018). Analysis of the complexity of the automatic pipeline generation problem. CEC 2018.
- Garciarena U, Santana R and Mendiburu A (2018). Deep neural networks for automatic pipeline generation with transfer learning. GECCO 2018.
- Vadillo J and Santana R (2019). Universal Adversarial Examples in Speech Command Classification. ICML Workshop 2019.
- Vadillo J and Santana R (2020). On the human evaluation of universal audio adversarial perturbations. Computers & Security.
- Vadillo J, Santana R and Lozano JA (2020). Universal adversarial perturbations for speech command classification. INTERSPEECH 2020.
- Vadillo J, Santana R and Lozano JA (2020). Rethinking the defense against adversarial examples using DNNs. IJCNN 2020.
- Vadillo J, Santana R and Lozano JA (2020). Adversarial examples: Attacks and defenses for deep learning models. arXiv.
- Vadillo J, Santana R and Lozano JA (2021). Extending adversarial attacks and defenses to deep 3D point cloud classifiers. Journal of Machine Learning Research.
- Vadillo J, Santana R and Lozano JA (2022). Open issues in adversarial machine learning. WIRES Data Mining and Knowledge Discovery.
- Garciarena U, Marti L and Santana R (2021). Adversarial Perturbations for Evolutionary Optimization. CEC 2021.
- Santana R, LarraΓ±aga P and Lozano JA (2010). Synergies between network-based representations and probabilistic graphical modeling in the solution of combinatorial optimization problems. J. Statistical Mechanics.